Field testing of a vaccine against eel diseases caused by Vibrio vulnificus

The field results of a vaccination programme against Vibrio vulnificus sero var E (biotype 2) in a Spanish eel farm are reported. A total of 9.5 millio n glass eels were vaccinated from January 1998 to March 2000 by prolonged i mmersion followed by 2 subsequent reimmunisations after 12 to 14 and 24 to 28 d, respectively. The acquired protection and the immune response against serovar E were estimated over a period of 6 mo after vaccination. A simila r vaccination schedule was conducted with elvers in a Danish eel farm, In t his case, the acquired protection and the immune response against serovar E and the new eel-pathogenic serovars, recently described in Denmark, were e valuated over a short term. The overall results show that the vaccine again st V. vulnificus serovar E induces a satisfactory protective immunity durin g the main growth period of eels (around 6 mo) with a relative percentage s urvival of 62 to 86% and protects them against the new eel-pathogenic serov ars, Vaccination of eels by immersion seems to be the best strategy to prev ent diseases caused by V. vulnificus.